function node_form_submit_build_node

Updates the form state's node entity by processing this submission's values.

This is the default builder function for the node form. It is called
during the "Save" and "Preview" submit handlers to retrieve the entity to
save or preview. This function can also be called by a "Next" button of a
wizard to update the form state's entity with the current step's values
before proceeding to the next step.